Kelly Green Sea Glass
The most obvious source of kelly green sea glass is Uncola bottles such as 7UP and Sprite etc. Liquor bottles are also a source along with basic household items.
When I first moved to Puerto Rico Heineken and Becks Beer were bottled in amber bottles. Kelly green sea glass was abundant at the time so it is safe to say that the lions share is not from these beer brands. They are now bottled there in the familiar green bottles and Heineken is affectionately nicknamed "Palmolive".
I have found this color to be the hardest to drill. I use to make sea glass filled mini bottle pendants and have had a harder time finding kelly green sea glass pieces that were small enough to fit in the bottles. I believe it is a strong glass and does not break into little pieces as easily as the other colors.
Various elements are used in glass making to create colors so glass colors differ in chemical makeup. Perhaps this makes some glass harder than others. Also some glass is annealed in the production process and some is not. Annealing hardens glass. So glass items do vary in strength.